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Math Help - Rotation of Axes to graph a quadratic equation with a xy term

  1. #1
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    Rotation of Axes to graph a quadratic equation with a xy term

    I need to graph:

    (x^2)+3xy+(y^2)=1

    but, using the cot(2theta)=(a-c)/b

    I got 0, and using

    cot = 0degrees

    or

    cot = 90degrees

    does not remove the xy term.

    please help!!!
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  2. #2
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    Quote Originally Posted by mathmana View Post
    I need to graph:

    (x^2)+3xy+(y^2)=1

    but, using the cot(2theta)=(a-c)/b

    I got 0, and using

    cot = 0degrees

    or

    cot = 90degrees

    does not remove the xy term.

    please help!!!
    \cot (2 \theta) = 0 \Rightarrow 2 \theta = 90^0 \Rightarrow \theta = 45^0.
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  3. #3
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    Yes, I figured that out yesterday.
    For some reason I thought cot was y/x.
    Thanks for responding anyway!!
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